Multi-radio coexistence

ABSTRACT

To comport with specific absorption rate (SAR) requirements for a transmitting multi-radio mobile device, transmissions of the multiple radios may be duplexed to ensure compliance with communication regulations. Duplexing of transmissions may occur if overall transmissions exceed a particular threshold value. The duplexing may be opportunistic or deterministic.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 U.S.C. §119(e) to UnitedStates Provisional Patent Application No. 61/576,296 entitled“MULTI-RADIO COEXISTENCE” filed on Dec. 15, 2011, the disclosure ofwhich is expressly incorporated herein by reference in its entirety.

BACKGROUND

1. Field

Aspects of the present disclosure relate generally to multi-radiotechniques and, more specifically, to coexistence techniques formulti-radio devices.

2. Background

Wireless communication systems are widely deployed to provide varioustypes of communication content such as voice, data, and so on. Thesesystems may be multiple-access systems capable of supportingcommunication with multiple users by sharing the available systemresources (e.g., bandwidth and transmit power). Examples of suchmultiple access systems include code division multiple access (CDMA)systems, time division multiple access (TDMA) systems, frequencydivision multiple access (FDMA) systems, 3GPP Long Term Evolution (LTE)systems, and orthogonal frequency division multiple access (OFDMA)systems.

Generally, a wireless multiple-access communication system cansimultaneously support communication for multiple wireless terminals.Each terminal communicates with one or more base stations viatransmissions on the forward and reverse links. The forward link (ordownlink) refers to the communication link from the base stations to theterminals, and the reverse link (or uplink) refers to the communicationlink from the terminals to the base stations. This communication linkmay be established via a single-in-single-out, multiple-in-single-out ora multiple-in-multiple out (MIMO) system.

Some conventional advanced devices include multiple radios fortransmitting/receiving using different Radio Access Technologies (RATs).Examples of RATs include, e.g., Universal Mobile TelecommunicationsSystem (UMTS), Global System for Mobile Communications (GSM), cdma2000,WiMAX, WLAN (e.g., WiFi), Bluetooth, LTE, and the like.

An example mobile device includes an LTE User Equipment (UE), such as afourth generation (4G) mobile phone. Such 4G phone may include variousradios to provide a variety of functions for the user. For purposes ofthis example, the 4G phone includes an LTE radio for voice and data, anIEEE 802.11 (WiFi) radio, a Global Positioning System (GPS) radio, and aBluetooth radio, where two of the above or all four may operatesimultaneously. While the different radios provide usefulfunctionalities for the phone, their inclusion in a single device givesrise to coexistence issues. Specifically, operation of one radio may insome cases interfere with operation of another radio through radiative,conductive, resource collision, and/or other interference mechanisms.Coexistence issues include such interference.

This is especially true for the LTE uplink channel, which is adjacent tothe Industrial Scientific and Medical (ISM) band and may causeinterference therewith. It is noted that Bluetooth and some Wirelesslocal area network (WLAN) channels fall within the ISM band. In someinstances, a Bluetooth error rate can become unacceptable when LTE isactive in some channels of Band 7 or even Band 40 for some Bluetoothchannel conditions. Even though there is no significant degradation toLTE, simultaneous operation with Bluetooth can result in disruption invoice services terminating in a Bluetooth headset. Such disruption maybe unacceptable to the consumer. A similar issue exists when LTEtransmissions interfere with GPS. Currently, there is no mechanism thatcan solve this issue since LTE by itself does not experience anydegradation

With reference specifically to LTE, it is noted that a UE communicateswith an evolved NodeB (eNB; e.g., a base station for a wirelesscommunications network) to inform the eNodeB of interference seen by theUE on the downlink. Furthermore, the eNodeB may be able to estimateinterference at the UE using a downlink error rate. In some instances,the eNodeB and the UE can cooperate to find a solution that reducesinterference at the UE, even interference due to radios within the UEitself. However, in conventional LTE, the interference estimatesregarding the downlink may not be adequate to comprehensively addressinterference.

In one instance, an LTE uplink signal interferes with a Bluetooth signalor WLAN signal. However, such interference is not reflected in thedownlink measurement reports at the eNodeB. As a result, unilateralaction on the part of the UE (e.g., moving the uplink signal to adifferent channel) may be thwarted by the eNodeB, which is not aware ofthe uplink coexistence issue and seeks to undo the unilateral action.For instance, even if the UE re-establishes the connection on adifferent frequency channel, the network can still handover the UE backto the original frequency channel that was corrupted by the in-deviceinterference. This is a likely scenario because the desired signalstrength on the corrupted channel may sometimes be higher than reflectedin the measurement reports of the new channel based on Reference SignalReceived Power (RSRP) to the eNodeB. Hence, a ping-pong effect of beingtransferred back and forth between the corrupted channel and the desiredchannel can happen if the eNodeB uses RSRP reports to make handoverdecisions.

Other unilateral action on the part of the UE, such as simply stoppinguplink communications without coordination of the eNodeB may cause powerloop malfunctions at the eNodeB. Additional issues that exist inconventional LTE include a general lack of ability on the part of the UEto suggest desired configurations as an alternative to configurationsthat have coexistence issues. For at least these reasons, uplinkcoexistence issues at the UE may remain unresolved for a long timeperiod, degrading performance and efficiency for other radios of the UE.

SUMMARY

In one aspect, a method of wireless communication is disclosed. Themethod includes measuring a transmit power from at least one radioaccess technology (RAT). The method also includes duplexingtransmissions of a first RAT with transmissions of a second RAT when themeasured transmit powers exceed a value associated with a specificabsorption rate (SAR) threshold value.

Another aspect discloses wireless communication having a memory and atleast one processor coupled to the memory. The processor(s) isconfigured to measure a transmit power from at least one radio accesstechnology (RAT). The processor(s) is also configured to duplextransmissions of a first RAT with transmissions of a second RAT when themeasured transmit powers exceed a value associated with a specificabsorption rate (SAR) threshold value.

In another aspect, a computer program product for wirelesscommunications in a wireless network having a non-transitorycomputer-readable medium is disclosed. The computer readable medium hasnon-transitory program code recorded thereon which, when executed by theprocessor(s), causes the processor(s) to perform operations of measuringa transmit power from at least one radio access technology (RAT). Theprogram code also causes the processor(s) to duplex transmissions of afirst RAT with transmissions of a second RAT when the measured transmitpowers exceed a value associated with a specific absorption rate (SAR)threshold value.

Another aspect discloses an apparatus including means for measuring atransmit power from at least one radio access technology (RAT). Theapparatus also includes means for duplexing transmissions of a first RATwith transmissions of a second RAT when the measured transmit powersexceed a value associated with a specific absorption rate (SAR)threshold value.

Additional features and advantages of the disclosure will be describedbelow. It should be appreciated by those skilled in the art that thisdisclosure may be readily utilized as a basis for modifying or designingother structures for carrying out the same purposes of the presentdisclosure. It should also be realized by those skilled in the art thatsuch equivalent constructions do not depart from the teachings of thedisclosure as set forth in the appended claims. The novel features,which are believed to be characteristic of the disclosure, both as toits organization and method of operation, together with further objectsand advantages, will be better understood from the following descriptionwhen considered in connection with the accompanying figures. It is to beexpressly understood, however, that each of the figures is provided forthe purpose of illustration and description only and is not intended asa definition of the limits of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The features, nature, and advantages of the present disclosure willbecome more apparent from the detailed description set forth below whentaken in conjunction with the drawings in which like referencecharacters identify correspondingly throughout.

FIG. 1 illustrates a multiple access wireless communication systemaccording to one aspect.

FIG. 2 is a block diagram of a communication system according to oneaspect.

FIG. 3 illustrates an exemplary frame structure in downlink Long TermEvolution (LTE) communications.

FIG. 4 is a block diagram conceptually illustrating an exemplary framestructure in uplink Long Term Evolution (LTE) communications.

FIG. 5 illustrates an example wireless communication environment.

FIG. 6 is a block diagram of an example design for a multi-radiowireless device.

FIG. 7 is graph showing respective potential collisions between sevenexample radios in a given decision period.

FIG. 8 is a diagram showing operation of an example Coexistence Manager(CxM) over time.

FIG. 9 is a block diagram illustrating adjacent frequency bands.

FIG. 10 is a block diagram of a system for providing support within awireless communication environment for multi-radio coexistencemanagement according to one aspect of the present disclosure.

FIG. 11 is a block diagram illustrating duplexing transmissions.

FIG. 12 is a block diagram illustrating power management according toone aspect of the present disclosure.

FIG. 13 is a diagram illustrating an example of a hardwareimplementation for an apparatus employing power management.

DETAILED DESCRIPTION

Various aspects of the disclosure provide techniques to energytransmission issues in multi-radio devices. In certain devices, such asmobile communication devices, governmental, or other bodies, such as theUnited States Federal Communication Commission (FCC), may regulate theamount of energy a device can transmit. For example, the FCC regulatesthe measure of the amount of radio frequency energy absorbed by thehuman body when using a mobile device. The amount of absorbed energy isreferred to as a specific absorption rate (SAR) value. To ensure safeexposure, the FCC requires cell phone manufacturers to ensure that theirphones comply with SAR threshold limits during operation. In amulti-radio mobile device, if transmissions of a first radio accesstechnology (RAT) overlap with transmissions of a second (or more)RAT(s), a SAR threshold limit may be exceeded. To avoid exceeding a SARlimit, transmissions of multiple radios may be duplexed in a mannerdescribed below.

The techniques described herein can be used for various wirelesscommunication networks such as Code Division Multiple Access (CDMA)networks, Time Division Multiple Access (TDMA) networks, FrequencyDivision Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA)networks, Single-Carrier FDMA (SC-FDMA) networks, etc. The terms“networks” and “systems” are often used interchangeably. A CDMA networkcan implement a radio technology such as Universal Terrestrial RadioAccess (UTRA), cdma2000, etc. UTRA includes Wideband-CDMA (W-CDMA) andLow Chip Rate (LCR). cdma2000 covers IS-2000, IS-95 and IS-856standards. A TDMA network can implement a radio technology such asGlobal System for Mobile Communications (GSM). An OFDMA network canimplement a radio technology such as Evolved UTRA (E-UTRA), IEEE 802.11,IEEE 802.16, IEEE 802.20, Flash-OFDM®, etc. UTRA, E-UTRA, and GSM arepart of Universal Mobile Telecommunication System (UMTS). Long TermEvolution (LTE) is an upcoming release of UMTS that uses E-UTRA. UTRA,E-UTRA, GSM, UMTS and LTE are described in documents from anorganization named “3^(rd) Generation Partnership Project” (3GPP).CDMA2000 is described in documents from an organization named “3^(rd)Generation Partnership Project 2” (3GPP2). These various radiotechnologies and standards are known in the art. For clarity, certainaspects of the techniques are described below for LTE, and LTEterminology is used in portions of the description below.

Single carrier frequency division multiple access (SC-FDMA), whichutilizes single carrier modulation and frequency domain equalization isa technique that can be utilized with various aspects described herein.SC-FDMA has similar performance and essentially the same overallcomplexity as those of an OFDMA system. SC-FDMA signal has lowerpeak-to-average power ratio (PAPR) because of its inherent singlecarrier structure. SC-FDMA has drawn great attention, especially in theuplink communications where lower PAPR greatly benefits the mobileterminal in terms of transmit power efficiency. It is currently aworking assumption for an uplink multiple access scheme in 3GPP LongTerm Evolution (LTE), or Evolved UTRA.

Referring to FIG. 1, a multiple access wireless communication systemaccording to one aspect is illustrated. An evolved Node B 100 (eNodeB)includes a computer 115 that has processing resources and memoryresources to manage the LTE communications by allocating resources andparameters, granting/denying requests from user equipment, and/or thelike. The eNodeB 100 also has multiple antenna groups, one groupincluding antenna 104 and antenna 106, another group including antenna108 and antenna 110, and an additional group including antenna 112 andantenna 114. In FIG. 1, only two antennas are shown for each antennagroup, however, more or fewer antennas can be utilized for each antennagroup. A User Equipment (UE) 116 (also referred to as an Access Terminal(AT)) is in communication with antennas 112 and 114, while antennas 112and 114 transmit information to the UE 116 over an uplink (UL) 188. TheUE 122 is in communication with antennas 106 and 108, while antennas 106and 108 transmit information to the UE 122 over a downlink (DL) 126 andreceive information from the UE 122 over an uplink 124. In a frequencydivision duplex (FDD) system, communication links 118, 120, 124 and 126can use different frequencies for communication. For example, thedownlink 120 can use a different frequency than used by the uplink 118.

Each group of antennas and/or the area in which they are designed tocommunicate is often referred to as a sector of the eNodeB. In thisaspect, respective antenna groups are designed to communicate to UEs ina sector of the areas covered by the eNodeB 100.

In communication over the downlinks 120 and 126, the transmittingantennas of the eNodeB 100 utilize beamforming to improve thesignal-to-noise ratio of the uplinks for the different UEs 116 and 122.Also, an eNodeB using beamforming to transmit to UEs scattered randomlythrough its coverage causes less interference to UEs in neighboringcells than a UE transmitting through a single antenna to all its UEs.

An eNodeB can be a fixed station used for communicating with theterminals and can also be referred to as an access point, base station,or some other terminology. A UE can also be called an access terminal, awireless communication device, terminal, or some other terminology.

FIG. 2 is a block diagram of an aspect of a transmitter system 210 (alsoknown as an eNodeB) and a receiver system 250 (also known as a UE) in aMIMO system 200. In some instances, both a UE and an eNodeB each have atransceiver that includes a transmitter system and a receiver system. Atthe transmitter system 210, traffic data for a number of data streams isprovided from a data source 212 to a transmit (TX) data processor 214.

A MIMO system employs multiple (N_(T)) transmit antennas and multiple(N_(R)) receive antennas for data transmission. A MIMO channel formed bythe N_(T) transmit and N_(R) receive antennas may be decomposed intoN_(S) independent channels, which are also referred to as spatialchannels, wherein N_(S)≦min{N_(T), N_(R)}. Each of the N_(S) independentchannels corresponds to a dimension. The MIMO system can provideimproved performance (e.g., higher throughput and/or greaterreliability) if the additional dimensionalities created by the multipletransmit and receive antennas are utilized.

A MIMO system supports time division duplex (TDD) and frequency divisionduplex (FDD) systems. In a TDD system, the uplink and downlinktransmissions are on the same frequency region so that the reciprocityprinciple allows the estimation of the downlink channel from the uplinkchannel. This enables the eNodeB to extract transmit beamforming gain onthe downlink when multiple antennas are available at the eNodeB.

In an aspect, each data stream is transmitted over a respective transmitantenna. The TX data processor 214 formats, codes, and interleaves thetraffic data for each data stream based on a particular coding schemeselected for that data stream to provide coded data.

The coded data for each data stream can be multiplexed with pilot datausing OFDM techniques. The pilot data is a known data pattern processedin a known manner and can be used at the receiver system to estimate thechannel response. The multiplexed pilot and coded data for each datastream is then modulated (e.g., symbol mapped) based on a particularmodulation scheme (e.g., BPSK, QPSK, M-PSK, or M-QAM) selected for thatdata stream to provide modulation symbols. The data rate, coding, andmodulation for each data stream can be determined by instructionsperformed by a processor 230 operating with a memory 232.

The modulation symbols for respective data streams are then provided toa TX MIMO processor 220, which can further process the modulationsymbols (e.g., for OFDM). The TX MIMO processor 220 then provides N_(T)modulation symbol streams to N_(T) transmitters (TMTR) 222 a through 222t. In certain aspects, the TX MIMO processor 220 applies beamformingweights to the symbols of the data streams and to the antenna from whichthe symbol is being transmitted.

Each transmitter 222 receives and processes a respective symbol streamto provide one or more analog signals, and further conditions (e.g.,amplifies, filters, and upconverts) the analog signals to provide amodulated signal suitable for transmission over the MIMO channel. N_(T)modulated signals from the transmitters 222 a through 222 t are thentransmitted from N_(T) antennas 224 a through 224 t, respectively.

At a receiver system 250, the transmitted modulated signals are receivedby N_(R) antennas 252 a through 252 r and the received signal from eachantenna 252 is provided to a respective receiver (RCVR) 254 a through254 r. Each receiver 254 conditions (e.g., filters, amplifies, anddownconverts) a respective received signal, digitizes the conditionedsignal to provide samples, and further processes the samples to providea corresponding “received” symbol stream.

An RX data processor 260 then receives and processes the N_(R) receivedsymbol streams from N_(R) receivers 254 based on a particular receiverprocessing technique to provide N_(R)“detected” symbol streams. The RXdata processor 260 then demodulates, deinterleaves, and decodes eachdetected symbol stream to recover the traffic data for the data stream.The processing by the RX data processor 260 is complementary to theprocessing performed by the TX MIMO processor 220 and the TX dataprocessor 214 at the transmitter system 210.

A processor 270 (operating with a memory 272) periodically determineswhich pre-coding matrix to use (discussed below). The processor 270formulates an uplink message having a matrix index portion and a rankvalue portion.

The uplink message can include various types of information regardingthe communication link and/or the received data stream. The uplinkmessage is then processed by a TX data processor 238, which alsoreceives traffic data for a number of data streams from a data source236, modulated by a modulator 280, conditioned by transmitters 254 athrough 254 r, and transmitted back to the transmitter system 210.

At the transmitter system 210, the modulated signals from the receiversystem 250 are received by antennas 224, conditioned by receivers 222,demodulated by a demodulator 240, and processed by an RX data processor242 to extract the uplink message transmitted by the receiver system250. The processor 230 then determines which pre-coding matrix to usefor determining the beamforming weights, then processes the extractedmessage.

FIG. 3 is a block diagram conceptually illustrating an exemplary framestructure in downlink Long Term Evolution (LTE) communications. Thetransmission timeline for the downlink may be partitioned into units ofradio frames. Each radio frame may have a predetermined duration (e.g.,10 milliseconds (ms)) and may be partitioned into 10 subframes withindices of 0 through 9. Each subframe may include two slots. Each radioframe may thus include 20 slots with indices of 0 through 19. Each slotmay include L symbol periods, e.g., 7 symbol periods for a normal cyclicprefix (as shown in FIG. 3) or 6 symbol periods for an extended cyclicprefix. The 2L symbol periods in each subframe may be assigned indicesof 0 through 2L−1. The available time frequency resources may bepartitioned into resource blocks. Each resource block may cover Nsubcarriers (e.g., 12 subcarriers) in one slot.

In LTE, an eNodeB may send a Primary Synchronization Signal (PSS) and aSecondary Synchronization Signal (SSS) for each cell in the eNodeB. ThePSS and SSS may be sent in symbol periods 6 and 5, respectively, in eachof subframes 0 and 5 of each radio frame with the normal cyclic prefix,as shown in FIG. 3. The synchronization signals may be used by UEs forcell detection and acquisition. The eNodeB may send a Physical BroadcastChannel (PBCH) in symbol periods 0 to 3 in slot 1 of subframe 0. ThePBCH may carry certain system information.

The eNodeB may send a Cell-specific Reference Signal (CRS) for each cellin the eNodeB. The CRS may be sent in symbols 0, 1, and 4 of each slotin case of the normal cyclic prefix, and in symbols 0, 1, and 3 of eachslot in case of the extended cyclic prefix. The CRS may be used by UEsfor coherent demodulation of physical channels, timing and frequencytracking, Radio Link Monitoring (RLM), Reference Signal Received Power(RSRP), and Reference Signal Received Quality (RSRQ) measurements, etc.

The eNodeB may send a Physical Control Format Indicator Channel (PCFICH)in the first symbol period of each subframe, as seen in FIG. 3. ThePCFICH may convey the number of symbol periods (M) used for controlchannels, where M may be equal to 1, 2 or 3 and may change from subframeto subframe. M may also be equal to 4 for a small system bandwidth,e.g., with less than 10 resource blocks. In the example shown in FIG. 3,M=3. The eNodeB may send a Physical HARQ Indicator Channel (PHICH) and aPhysical Downlink Control Channel (PDCCH) in the first M symbol periodsof each subframe. The PDCCH and PHICH are also included in the firstthree symbol periods in the example shown in FIG. 3. The PHICH may carryinformation to support Hybrid Automatic Repeat Request (HARQ). The PDCCHmay carry information on resource allocation for UEs and controlinformation for downlink channels. The eNodeB may send a PhysicalDownlink Shared Channel (PDSCH) in the remaining symbol periods of eachsubframe. The PDSCH may carry data for UEs scheduled for datatransmission on the downlink. The various signals and channels in LTEare described in 3GPP TS 36.211, entitled “Evolved Universal TerrestrialRadio Access (E-UTRA); Physical Channels and Modulation,” which ispublicly available.

The eNodeB may send the PSS, SSS and PBCH in the center 1.08 MHz of thesystem bandwidth used by the eNodeB. The eNodeB may send the PCFICH andPHICH across the entire system bandwidth in each symbol period in whichthese channels are sent. The eNodeB may send the PDCCH to groups of UEsin certain portions of the system bandwidth. The eNodeB may send thePDSCH to specific UEs in specific portions of the system bandwidth. TheeNodeB may send the PSS, SSS, PBCH, PCFICH and PHICH in a broadcastmanner to all UEs, may send the PDCCH in a unicast manner to specificUEs, and may also send the PDSCH in a unicast manner to specific UEs.

A number of resource elements may be available in each symbol period.Each resource element may cover one subcarrier in one symbol period andmay be used to send one modulation symbol, which may be a real orcomplex value. Resource elements not used for a reference signal in eachsymbol period may be arranged into resource element groups (REGs). EachREG may include four resource elements in one symbol period. The PCFICHmay occupy four REGs, which may be spaced approximately equally acrossfrequency, in symbol period 0. The PHICH may occupy three REGs, whichmay be spread across frequency, in one or more configurable symbolperiods. For example, the three REGs for the PHICH may all belong insymbol period 0 or may be spread in symbol periods 0, 1 and 2. The PDCCHmay occupy 9, 18, 32 or 64 REGs, which may be selected from theavailable REGs, in the first M symbol periods. Only certain combinationsof REGs may be allowed for the PDCCH.

A UE may know the specific REGs used for the PHICH and the PCFICH. TheUE may search different combinations of REGs for the PDCCH. The numberof combinations to search is typically less than the number of allowedcombinations for the PDCCH. An eNodeB may send the PDCCH to the UE inany of the combinations that the UE will search.

FIG. 4 is a block diagram conceptually illustrating an exemplary framestructure in uplink Long Term Evolution (LTE) communications. Theavailable Resource Blocks (RBs) for the uplink may be partitioned into adata section and a control section. The control section may be formed atthe two edges of the system bandwidth and may have a configurable size.The resource blocks in the control section may be assigned to UEs fortransmission of control information. The data section may include allresource blocks not included in the control section. The design in FIG.4 results in the data section including contiguous subcarriers, whichmay allow a single UE to be assigned all of the contiguous subcarriersin the data section.

A UE may be assigned resource blocks in the control section to transmitcontrol information to an eNodeB. The UE may also be assigned resourceblocks in the data section to transmit data to the eNodeB. The UE maytransmit control information in a Physical Uplink Control Channel(PUCCH) on the assigned resource blocks in the control section. The UEmay transmit only data or both data and control information in aPhysical Uplink Shared Channel (PUSCH) on the assigned resource blocksin the data section. An uplink transmission may span both slots of asubframe and may hop across frequency as shown in FIG. 4.

The PSS, SSS, CRS, PBCH, PUCCH and PUSCH in LTE are described in 3GPP TS36.211, entitled “Evolved Universal Terrestrial Radio Access (E-UTRA);Physical Channels and Modulation,” which is publicly available.

In an aspect, described herein are systems and methods for providingsupport within a wireless communication environment, such as a 3GPP LTEenvironment or the like, to facilitate multi-radio coexistencesolutions.

Referring now to FIG. 5, illustrated is an example wirelesscommunication environment 500 in which various aspects described hereincan function. The wireless communication environment 500 can include awireless device 510, which can be capable of communicating with multiplecommunication systems. These systems can include, for example, one ormore cellular systems 520 and/or 530, one or more WLAN systems 540and/or 550, one or more wireless personal area network (WPAN) systems560, one or more broadcast systems 570, one or more satellitepositioning systems 580, other systems not shown in FIG. 5, or anycombination thereof. It should be appreciated that in the followingdescription the terms “network” and “system” are often usedinterchangeably.

The cellular systems 520 and 530 can each be a CDMA, TDMA, FDMA, OFDMA,Single Carrier FDMA (SC-FDMA), or other suitable system. A CDMA systemcan implement a radio technology such as Universal Terrestrial RadioAccess (UTRA), cdma2000, etc. UTRA includes Wideband CDMA (WCDMA) andother variants of CDMA. Moreover, cdma2000 covers IS-2000 (CDMA2000 1X),IS-95 and IS-856 (HRPD) standards. A TDMA system can implement a radiotechnology such as Global System for Mobile Communications (GSM),Digital Advanced Mobile Phone System (D-AMPS), etc. An OFDMA system canimplement a radio technology such as Evolved UTRA (E-UTRA), Ultra MobileBroadband (UMB), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDM®, etc.UTRA and E-UTRA are part of Universal Mobile Telecommunication System(UMTS). 3GPP Long Term Evolution (LTE) and LTE-Advanced (LTE-A) are newreleases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSMare described in documents from an organization named “3^(rd) GenerationPartnership Project” (3GPP). cdma2000 and UMB are described in documentsfrom an organization named “3^(rd) Generation Partnership Project 2”(3GPP2). In an aspect, the cellular system 520 can include a number ofbase stations 522, which can support bi-directional communication forwireless devices within their coverage. Similarly, the cellular system530 can include a number of base stations 532 that can supportbi-directional communication for wireless devices within their coverage.

WLAN systems 540 and 550 can respectively implement radio technologiessuch as IEEE 802.11 (WiFi), Hiperlan, etc. The WLAN system 540 caninclude one or more access points 542 that can support bi-directionalcommunication. Similarly, the WLAN system 550 can include one or moreaccess points 552 that can support bi-directional communication. TheWPAN system 560 can implement a radio technology such as Bluetooth (BT),IEEE 802.15, etc. Further, the WPAN system 560 can supportbi-directional communication for various devices such as wireless device510, a headset 562, a computer 564, a mouse 566, or the like.

The broadcast system 570 can be a television (TV) broadcast system, afrequency modulation (FM) broadcast system, a digital broadcast system,etc. A digital broadcast system can implement a radio technology such asMediaFLO™, Digital Video Broadcasting for Handhelds (DVB-H), IntegratedServices Digital Broadcasting for Terrestrial Television Broadcasting(ISDB-T), or the like. Further, the broadcast system 570 can include oneor more broadcast stations 572 that can support one-way communication.

The satellite positioning system 580 can be the United States GlobalPositioning System (GPS), the European Galileo system, the RussianGLONASS system, the Quasi-Zenith Satellite System (QZSS) over Japan, theIndian Regional Navigational Satellite System (IRNSS) over India, theBeidou system over China, and/or any other suitable system. Further, thesatellite positioning system 580 can include a number of satellites 582that transmit signals for position determination.

In an aspect, the wireless device 510 can be stationary or mobile andcan also be referred to as a user equipment (UE), a mobile station, amobile equipment, a terminal, an access terminal, a subscriber unit, astation, etc. The wireless device 510 can be cellular phone, a personaldigital assistance (PDA), a wireless modem, a handheld device, a laptopcomputer, a cordless phone, a wireless local loop (WLL) station, etc. Inaddition, a wireless device 510 can engage in two-way communication withthe cellular system 520 and/or 530, the WLAN system 540 and/or 550,devices with the WPAN system 560, and/or any other suitable systems(s)and/or devices(s). The wireless device 510 can additionally oralternatively receive signals from the broadcast system 570 and/orsatellite positioning system 580. In general, it can be appreciated thatthe wireless device 510 can communicate with any number of systems atany given moment. Also, the wireless device 510 may experiencecoexistence issues among various ones of its constituent radio devicesthat operate at the same time. Accordingly, device 510 includes acoexistence manager (CxM, not shown) that has a functional module todetect and mitigate coexistence issues, as explained further below.

Turning next to FIG. 6, a block diagram is provided that illustrates anexample design for a multi-radio wireless device 600 and may be used asan implementation of the radio 510 of FIG. 5. As FIG. 6 illustrates, thewireless device 600 can include N radios 620 a through 620 n, which canbe coupled to N antennas 610 a through 610 n, respectively, where N canbe any integer value. It should be appreciated, however, that respectiveradios 620 can be coupled to any number of antennas 610 and thatmultiple radios 620 can also share a given antenna 610.

In general, a radio 620 can be a unit that radiates or emits energy inan electromagnetic spectrum, receives energy in an electromagneticspectrum, or generates energy that propagates via conductive means. Byway of example, a radio 620 can be a unit that transmits a signal to asystem or a device or a unit that receives signals from a system ordevice. Accordingly, it can be appreciated that a radio 620 can beutilized to support wireless communication. In another example, a radio620 can also be a unit (e.g., a screen on a computer, a circuit board,etc.) that emits noise, which can impact the performance of otherradios. Accordingly, it can be further appreciated that a radio 620 canalso be a unit that emits noise and interference without supportingwireless communication.

In an aspect, respective radios 620 can support communication with oneor more systems. Multiple radios 620 can additionally or alternativelybe used for a given system, e.g., to transmit or receive on differentfrequency bands (e.g., cellular and PCS bands).

In another aspect, a digital processor 630 can be coupled to radios 620a through 620 n and can perform various functions, such as processingfor data being transmitted or received via the radios 620. Theprocessing for each radio 620 can be dependent on the radio technologysupported by that radio and can include encryption, encoding,modulation, etc., for a transmitter; demodulation, decoding, decryption,etc., for a receiver, or the like. In one example, the digital processor630 can include a coexistence manager (CxM) 640 that can controloperation of the radios 620 in order to improve the performance of thewireless device 600 as generally described herein. The coexistencemanager 640 can have access to a database 644, which can storeinformation used to control the operation of the radios 620. Asexplained further below, the coexistence manager 640 can be adapted fora variety of techniques to decrease interference between the radios. Inone example, the coexistence manager 640 requests a measurement gappattern or DRX cycle that allows an ISM radio to communicate duringperiods of LTE inactivity.

For simplicity, digital processor 630 is shown in FIG. 6 as a singleprocessor. However, it should be appreciated that the digital processor630 can include any number of processors, controllers, memories, etc. Inone example, a controller/processor 650 can direct the operation ofvarious units within the wireless device 600. Additionally oralternatively, a memory 652 can store program codes and data for thewireless device 600. The digital processor 630, controller/processor650, and memory 652 can be implemented on one or more integratedcircuits (ICs), application specific integrated circuits (ASICs), etc.By way of specific, non-limiting example, the digital processor 630 canbe implemented on a Mobile Station Modem (MSM) ASIC.

In an aspect, the coexistence manager 640 can manage operation ofrespective radios 620 utilized by wireless device 600 in order to avoidinterference and/or other performance degradation associated withcollisions between respective radios 620. coexistence manager 640 mayperform one or more processes, such as those illustrated in FIG. 10. Byway of further illustration, a graph 700 in FIG. 7 represents respectivepotential collisions between seven example radios in a given decisionperiod. In the example shown in graph 700, the seven radios include aWLAN transmitter (Tw), an LTE transmitter (Tl), an FM transmitter (Tf),a GSM/WCDMA transmitter (Tc/Tw), an LTE receiver (Rl), a Bluetoothreceiver (Rb), and a GPS receiver (Rg). The four transmitters arerepresented by four nodes on the left side of the graph 700. The fourreceivers are represented by three nodes on the right side of the graph700.

A potential collision between a transmitter and a receiver isrepresented on the graph 700 by a branch connecting the node for thetransmitter and the node for the receiver. Accordingly, in the exampleshown in the graph 700, collisions may exist between (1) the WLANtransmitter (Tw) and the Bluetooth receiver (Rb); (2) the LTEtransmitter (Tl) and the Bluetooth receiver (Rb); (3) the WLANtransmitter (Tw) and the LTE receiver (Rl); (4) the FM transmitter (Tf)and the GPS receiver (Rg); (5) a WLAN transmitter (Tw), a GSM/WCDMAtransmitter (Tc/Tw), and a GPS receiver (Rg).

In one aspect, an example coexistence manager 640 can operate in time ina manner such as that shown by diagram 800 in FIG. 8. As diagram 800illustrates, a timeline for coexistence manager operation can be dividedinto Decision Units (DUs), which can be any suitable uniform ornon-uniform length (e.g., 100 μs) where notifications are processed, anda response phase (e.g., 20 μs) where commands are provided to variousradios 620 and/or other operations are performed based on actions takenin the evaluation phase. In one example, the timeline shown in thediagram 800 can have a latency parameter defined by a worst caseoperation of the timeline, e.g., the timing of a response in the casethat a notification is obtained from a given radio immediately followingtermination of the notification phase in a given DU.

As shown in FIG. 9, Long Term Evolution (LTE) in band 7 (for frequencydivision duplex (FDD) uplink), band 40 (for time division duplex (TDD)communication), and band 38 (for TDD downlink) is adjacent to the 2.4GHz Industrial Scientific and Medical (ISM) band used by Bluetooth (BT)and Wireless Local Area Network (WLAN) technologies. Frequency planningfor these bands is such that there is limited or no guard bandpermitting traditional filtering solutions to avoid interference atadjacent frequencies. For example, a 20 MHz guard band exists betweenISM and band 7, but no guard band exists between ISM and band 40.

To be compliant with appropriate standards, communication devicesoperating over a particular band are to be operable over the entirespecified frequency range. For example, in order to be LTE compliant, amobile station/user equipment should be able to communicate across theentirety of both band 40 (2300-2400 MHz) and band 7 (2500-2570 MHz) asdefined by the 3rd Generation Partnership Project (3GPP). Without asufficient guard band, devices employ filters that overlap into otherbands causing band interference. Because band 40 filters are 100 MHzwide to cover the entire band, the rollover from those filters crossesover into the ISM band causing interference. Similarly, ISM devices thatuse the entirety of the ISM band (e.g., from 2401 through approximately2480 MHz) will employ filters that rollover into the neighboring band 40and band 7 and may cause interference.

In-device coexistence problems can exist with respect to a UE betweenresources such as, for example, LTE and ISM bands (e.g., forBluetooth/WLAN). In current LTE implementations, any interference issuesto LTE are reflected in the downlink measurements (e.g., ReferenceSignal Received Quality (RSRQ) metrics, etc.) reported by a UE and/orthe downlink error rate which the eNodeB can use to make inter-frequencyor inter-RAT handoff decisions to, e.g., move LTE to a channel or RATwith no coexistence issues. However, it can be appreciated that theseexisting techniques will not work if, for example, the LTE uplink iscausing interference to Bluetooth/WLAN but the LTE downlink does not seeany interference from Bluetooth/WLAN. More particularly, even if the UEautonomously moves itself to another channel on the uplink, the eNodeBcan in some cases handover the UE back to the problematic channel forload balancing purposes. In any case, it can be appreciated thatexisting techniques do not facilitate use of the bandwidth of theproblematic channel in the most efficient way.

Referring to FIG. 10, a block diagram of a system 1000 for providingsupport within a wireless communication environment for multi-radiocoexistence management is illustrated. In an aspect, the system 1000 caninclude one or more UEs 1010 and/or eNodeBs 1040, which can engage inuplink and/or downlink communications, and/or any other suitablecommunication with each other and/or any other entities in the system1000. In one example, the UE 1010 and/or eNodeB 1040 can be operable tocommunicate using a variety resources, including frequency channels andsub-bands, some of which can potentially be colliding with other radioresources (e.g., a broadband radio such as an LTE modem). Thus, the UE1010 can utilize various techniques for managing coexistence betweenmultiple radios utilized by the UE 1010, as generally described herein.

To mitigate at least the above shortcomings, the UE 1010 can utilizerespective features described herein and illustrated by the system 1000to facilitate support for multi-radio coexistence within the UE 1010.For example, a measuring module 1012, and a duplexing module 1014 can beprovided. The measuring module measures a transmit power from at leastone radio access technology (RAT). The duplexing module duplexes (usingeither time domain or frequency domain duplexing) transmissions of afirst RAT with transmissions of a second RAT when the measured transmitpowers exceeds a threshold value associated with a specific absorptionrate (SAR) threshold value.

When multiple radios of a device are in use, and if each radio istransmitting at a sufficiently high power, then the combined radios mayviolate the SAR limit. Concurrent use cases include when a cellular(e.g., LTE, GSM, or TD-SCDMA) based radio access technology (RAT) and aWLAN (e.g., WiFi) based radio access technology are active at the sametime. The concurrent use may cause the mobile device to exceed SARlimits. In particular, one example is for the softAP (soft access point)case, where the cellular radio is used as the backhaul link and WiFi isused as the access link to serve other stations. One aspect of thepresent disclosure is directed to power management so that a UEtransmitting both WiFi and LTE signals complies with the SARrestrictions during operation.

FIG. 11 illustrates an example of power management applied to a wirelesssystem having time division LTE (TD-LTE) and WLAN (e.g., WiFi)transmission. For TD-LTE, each LTE radio frame is configured with acertain downlink period (e.g., 3 ms) followed by a certain uplink period(e.g., 2 ms). In one aspect of the present disclosure, WLAN transactionsoccur only in the LTE downlink portion (e.g., WiFi is active). Duringthe LTE uplink portion, WLAN is not transmitting (e.g., WiFi isinactive). By structuring the transmission of one radio during timeswhen the other radio is not transmitting, the overall energy transmittedby the mobile device is reduced. This deterministic time divisionduplexing allows the WLAN and the LTE radios individually to transmitusing full power and still permit the mobile device to comply withoverall SAR requirements. In one aspect, the power management isopportunistic such that a first radio access technology transmits when asecond radio access technology is not transmitting (such as a transmittime period which is not currently being used), in addition to the timeperiods when the UE is not configured to transmit on LTE.

Various techniques may be applied to ensure that WiFi is activelytransmitting only during LTE downlink transmission time periods. In onetechnique, when the UE is operating as a WiFi station (STA), the UE WiFitransmitter in put in a power save mode. Once the station is in thepower save mode, it can wake up during LTE downlink time periods toreceive packets from the access point. In one aspect, the station knowsthe configured LTE timeline and the WiFi radio only retrieves downlinkpackets during the LTE downlink period by using power save (PS)-POLLmessages. The (PS)-POLL message may be sent a guard time ahead of thestart of the LTE uplink transmission to ensure there is sufficient timeto receive the downlink packet and send the ACK before the LTE uplinktransmission. By timing the PS-POLL messages this way, the WiFitransmitter only transmits uplink packets during the LTE downlinkperiod.

In another technique, when the UE is operating as an access point(softAP), a (clear to send) CTS-to-Self message is used to ensure WiFiuplink transmissions occur during the LTE downlink time periods. Inparticular, before the LTE uplink period begins, the WiFi transmittersends out a CTS-to-Self message, instructing the remote stations not totransmit to the UE during the LTE uplink time period. The CTS-to-Selfmessage may be prepared a guard time ahead of the start of the LTEuplink transmission to ensure there is sufficient time for contentionbefore the message is sent. The timing of the CTS-self message ensuresthat no acknowledgements are transmitted during the LTE uplink timeperiod.

When the UE is operating as a peer-to-peer (P2P) group owner or client(e.g., in accordance with WiFi Direct operation), a Notice of Absence(NOA) message may be used to control the WiFi traffic. The notice ofabsence message is sent by the P2P group owner to the P2P client tonotify the P2P-client about the absence periods during which P2P groupowner will not be available. The P2P group owner can use the NOA messageto indicate its periodic sleep/awake cycle to the P2P clients such thatP2P group owner and clients only wake up during the LTE downlink portion(i.e., no WLAN traffic occurs during the LTE uplink portion).Additionally, the NOA message may be sent on every beacon. Inparticular, in one configuration, the NOA message is sent a guard timeahead of the uplink transmission and the message includes the durationof the absence.

In one aspect, WiFi uplink transmission is not always constrained to theLTE downlink time periods. In particular, the duplexing occurs only whenthe LTE transmission (TX) power is high enough so that if the WiFi radiotransmits in the LTE uplink time period, the WiFi transmit power willexceed SAR limits. In a further aspect, if reducing the WiFi transmitpower may lead to more throughput loss than constraining WiFitransmission to LTE downlink periods only, then WiFi is constrained tothe LTE downlink time period. Although the previous discussion wasprimarily with respect to time division duplexing (TDD), the presentdisclosure is also applicable to frequency division duplexing (FDD).With FDD, the WiFi transmitter is permitted to send uplink packets whenthe LTE transmitter is not using its sub frames.

FIG. 12 illustrates a method for managing power. In block 1201, a UEmeasures the transmit power from at least one radio access technology(RAT). In block 1202, the UE duplexes transmissions of a first RAT withtransmissions of a second RAT when the measured transmit power exceeds athreshold value associated with a SAR threshold value.

FIG. 13 is a diagram illustrating an example of a hardwareimplementation for an apparatus 1300 employing a power management system1314. The power management system 1314 may be implemented with a busarchitecture, represented generally by a bus 1324. The bus 1324 mayinclude any number of interconnecting buses and bridges depending on thespecific application of the power management system 1314 and the overalldesign constraints. The bus 1324 links together various circuitsincluding one or more processors and/or hardware modules, represented bya processor 1326, a measuring module 1302, a duplexing module 1304 and acomputer-readable medium 1328. The bus 1324 may also link various othercircuits such as timing sources, peripherals, voltage regulators, andpower management circuits, which are well known in the art, andtherefore, will not be described any further.

The apparatus includes the power management system 1314 coupled to atransceiver 1322. The transceiver 1322 is coupled to one or moreantennas 1320. The transceiver 1322 provides a means for communicatingwith various other apparatus over a transmission medium. The powermanagement system 1314 includes the processor 1326 coupled to thecomputer-readable medium 1328. The processor 1326 is responsible forgeneral processing, including the execution of software stored on thecomputer-readable medium 1328. The software, when executed by theprocessor 1326, causes the power management system 1314 to perform thevarious functions described supra for any particular apparatus. Thecomputer-readable medium 1328 may also be used for storing data that ismanipulated by the processor 1326 when executing software. The powermanagement system 1314 further includes the measuring module 1302 formeasuring a transmit power and the duplexing module 1304 for duplexingtransmission of a first RAT with transmissions of a second RAT. Themeasuring module 1302 the duplexing module 1306 may be software modulesrunning in the processor 1326, resident/stored in the computer readablemedium 1328, one or more hardware modules coupled to the processor 1326,or some combination thereof. The power management system 1314 may be acomponent of the UE 250 and may include the memory 272 and/or theprocessor 270.

In one configuration, the apparatus 1300 for wireless communicationincludes means for measuring. The means may be the measuring module 1302and/or the power management system 1314 of the apparatus 1300 configuredto perform the functions recited by the measuring means. In one aspect,the aforementioned means for measuring may be the processor 270, memory272, coexistence manager 640, and/or measuring module 1012 configured toperform the functions recited by the aforementioned means.

In one configuration, the apparatus 1300 for wireless communicationincludes means for duplexing. The means may be the duplexing module 1304and/or the power management system 1314 of the apparatus 1300 configuredto perform the functions recited by the duplexing means. In one aspect,the aforementioned means for duplexing may be the processor 270, memory272, coexistence manager 640, and/or duplexing module 1014 configured toperform the functions recited by the aforementioned means. In anotheraspect, the aforementioned means may be any module or any apparatusconfigured to perform the functions recited by the aforementioned means.

The examples above describe aspects implemented in an LTE system.However, the scope of the disclosure is not so limited. Various aspectsmay be adapted for use with other communication systems, such as thosethat employ any of a variety of communication protocols including, butnot limited to, CDMA systems, TDMA systems, FDMA systems, and OFDMAsystems.

It is understood that the specific order or hierarchy of steps in theprocesses disclosed is an example of exemplary approaches. Based upondesign preferences, it is understood that the specific order orhierarchy of steps in the processes may be rearranged while remainingwithin the scope of the present disclosure. The accompanying methodclaims present elements of the various steps in a sample order, and arenot meant to be limited to the specific order or hierarchy presented.

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, circuits, and algorithm steps described inconnection with the aspects disclosed herein may be implemented aselectronic hardware, computer software, or combinations of both. Toclearly illustrate this interchangeability of hardware and software,various illustrative components, blocks, modules, circuits, and stepshave been described above generally in terms of their functionality.Whether such functionality is implemented as hardware or softwaredepends upon the particular application and design constraints imposedon the overall system. Skilled artisans may implement the describedfunctionality in varying ways for each particular application, but suchimplementation decisions should not be interpreted as causing adeparture from the scope of the present disclosure.

The various illustrative logical blocks, modules, and circuits describedin connection with the aspects disclosed herein may be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with theaspects disclosed herein may be embodied directly in hardware, in asoftware module executed by a processor, or in a combination of the two.A software module may reside in RAM memory, flash memory, ROM memory,EPROM memory, EEPROM memory, registers, hard disk, a removable disk, aCD-ROM, or any other form of storage medium known in the art. Anexemplary storage medium is coupled to the processor such the processorcan read information from, and write information to, the storage medium.In the alternative, the storage medium may be integral to the processor.The processor and the storage medium may reside in an ASIC. The ASIC mayreside in a user terminal. In the alternative, the processor and thestorage medium may reside as discrete components in a user terminal.

The previous description of the disclosed aspects is provided to enableany person skilled in the art to make or use the present disclosure.Various modifications to these aspects will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other aspects without departing from the spirit or scope ofthe disclosure. Thus, the present disclosure is not intended to belimited to the aspects shown herein but is to be accorded the widestscope consistent with the principles and novel features disclosedherein.

What is claimed is:
 1. A method for wireless communications in a userequipment, said method comprising: measuring a transmit power from atleast one radio access technology (RAT); and duplexing transmissions ofa first RAT with transmissions of a second RAT, such that the first RATtransmits when the second RAT is not transmitting, when the measuredtransmit powers exceed a value associated with a specific absorptionrate (SAR) threshold value and when reducing the transmit power from atleast one RAT would result in lower throughput than duplexing thetransmissions of the first RAT with the transmission of the second RAT.2. The method of claim 1, in which the measuring comprises measuring afirst transmit power from the first RAT and measuring a second transmitpower from the second RAT; and in which duplexing further comprisesduplexing transmissions of the first RAT with transmissions of thesecond RAT when a sum of the measured transmit powers exceeds thespecific absorption rate (SAR) threshold value.
 3. The method of claim1, in which duplexing is time division duplexing.
 4. The method of claim3 in which the first RAT is a time division duplexed (TDD) RAT and inwhich transmitting by the second RAT is confined to a receive time ofthe first RAT.
 5. The method of claim 1, in which duplexing isopportunistic.
 6. The method of claim 1, in which duplexing isdeterministic.
 7. An apparatus for wireless communication, comprising: amemory storing a program; and at least one processor coupled to thememory, the at least one processor being configured to perform thefollowing upon executing the program: to measure a transmit power fromat least one radio access technology (RAT); and to duplex transmissionsof a first RAT with transmissions of a second RAT, such that the firstRAT transmits when the second RAT is not transmitting, when the measuredtransmit powers exceed a value associated with a specific absorptionrate (SAR) threshold value and when reducing the transmit power from atleast one RAT would result in lower throughput than duplexing thetransmissions of the first RAT with the transmission of the second RAT.8. The apparatus of claim 7, in which the at least one processor isconfigured to measure by measuring a first transmit power from the firstRAT and measuring a second transmit power from the second RAT; and theat least one processor is configured to duplex by duplexingtransmissions of the first RAT with transmissions of the second RAT whena sum of the measured transmit powers exceeds the specific absorptionrate (SAR) threshold value.
 9. The apparatus of claim 7, in the at leastone processor is configured to duplex by time division duplexing. 10.The apparatus of claim 9, in which the first RAT is a time divisionduplexed (TDD) RAT and in which transmitting by the second RAT isconfined to a receive time of the first RAT.
 11. The apparatus of claim7, in which the at least one processor is configured toopportunistically duplex.
 12. The apparatus of claim 7, in which the atleast one processor is configured to is deterministically duplex.
 13. Acomputer program product for wireless communication in a wirelessnetwork, said computer program product comprising: a non-transitorycomputer-readable medium storing non-transitory program code which whenexecuted by a processor performs the following: measuring a transmitpower from at least one radio access technology (RAT); and duplexingtransmissions of a first RAT with transmissions of a second RAT, suchthat the first RAT transmits when the second RAT is not transmitting,when the measured transmit powers exceed a value associated with aspecific absorption rate (SAR) threshold value and when reducing thetransmit power from at least one RAT would result in lower throughputthan duplexing the transmissions of the first RAT with the transmissionof the second RAT.
 14. The computer program product of claim 13, inwhich the measuring comprises measuring a transmit power from at leastone radio access technology (RAT); and in which the duplexing furthercomprises duplexing transmissions of the first RAT with transmissions ofthe second RAT when the measured transmit powers exceeds a valueassociated with a specific absorption rate (SAR) threshold value.
 15. Anapparatus for wireless communication, said apparatus comprising: meansfor measuring a transmit power from at least one radio access technology(RAT); and means for duplexing transmissions of a first RAT withtransmissions of a second RAT, such that the first RAT transmits whenthe second RAT is not transmitting, when the measured transmit powersexceed a value associated with a specific absorption rate (SAR)threshold value and when reducing the transmit power from at least oneRAT would result in lower throughput than duplexing the transmissions ofthe first RAT with the transmission of the second RAT.
 16. The apparatusof claim 15, in which the means for duplexing is opportunistic ordeterministic.